I built a cross-platform reselling toolkit solo — 25+ users in 3 weeks, here's what actually worked

I'm a reseller. I was spending 20+ minutes per sourcing decision — eBay in one tab, Depop in another, Poshmark in a third, then manually subtracting fees on a calculator before I even knew if a flip was worth it. I built ResellReady to replace that entire workflow.

What it does

• Pulls 90-day sold comps from 6 platforms (eBay, Depop, Mercari, Poshmark, Grailed, Vinted) in one search

• Automatically deducts platform fees + payment processing — shows true net profit, not gross

• Searches wholesale suppliers on Alibaba, Made-in-China, Global Sources, and 1688 simultaneously

• 90-day sourcing calendar for seasonal demand planning

Stack: Flask, Firestore, Stripe, deployed on Render. No React. No Next.js. Just Python and vanilla JS — I move faster this way.

What worked

1. Solving my own problem. I wasn't guessing at what resellers needed — I was one. Every feature came from a real friction point I hit sourcing.

2. Going niche first. Instead of "tool for all sellers," I built solution pages targeting specific keywords — sneaker reselling tracker, vintage clothing margins, pallet liquidation ROI. Organic search traffic started before I ran a single ad.

3. Shipping fast. The MVP was a price-check + fee calc. No inventory, no calendar, no sourcing. I shipped that in about 3 weeks and added features based on what early users asked for.

What I'd do differently

Start the guest post and backlink outreach earlier. SEO compounds — every week you're not building domain authority is a week behind.

Where it stands now

25+ registered users, $49.99 MRR. Free plan is the main growth driver — resellers try the free checks, hit the limit, and upgrade for supplier sourcing.

If you're building in the reselling / recommerce space, happy to compare notes.

Christian, founder of ResellReady (resell-ready.com)